Korean Journal of Orthodontics最新文献

Objective: The purpose of this research was to analyze the three-dimensional forces acting on the mandibular teeth with aligner activation for distalization and an antitipping design of the mandibular canines, based on various pretreatment canine tips in vitro.

Methods: Five sets of clear aligners were designed to produce the same 0.25 mm distalization forces, with/without the 2° antitipping design, and were applied to canines with three initial angulations. Each group consisted of 12 aligners. Aligner forces were measured in real time using a force transducer measurement system.

Results: In the mesial group, the canines mainly received distal and extrusive forces; labial and intrusive forces were observed on the incisors, and the second premolar received mesial forces. In the upright and distal groups, the canines were subjected to distal and intrusive forces, while the incisors were subjected to lingual and extrusive forces. Greater mesial forces on the second premolars were also observed. In the upright and distal groups, the distal and intrusive forces on the canines, and the lingual and extrusive forces on the incisors, were reduced by adding a 2° antitipping design to the canines; however, the mesial and intrusive forces on the second premolars increased.

Conclusions: With clear aligners, the "bowing effect" is aggravated when the initial angulation of the canines is distal. This effect can be partially relieved by implementing an antitipping design on the canines, although greater attention should be paid to posterior anchorage control.

Objective: To investigate the pattern of change in force and moment according to the amounts of labial tipping and the material types of clear aligners (CA).

Methods: A 3D-printed maxillary typodont system, including crown, root, and periodontal ligament space, was constructed. Six groups were established based on the amount of labial tipping of #12 (0.3 mm and 0.6 mm), and the material types (Zendura [thermoplastic, one-layer, 0.75 mm], Trioclear [thermoplastic, three-layer, 0.5 mm], and Graphy TA-28 [direct printing, 0.5 mm]) (n = 6/group). A six-axis mechanical sensor apparatus was connected to the roots. Force and moment were measured after seating the CA in a 37°C water bath.

Results: When comparing 0.3 mm and 0.6 mm tipping, #12 showed an increase in labial inclination moment (Lab-inclination moment) in Zendura (P < 0.05); a decrease in labial force and an increase in Lab-inclination-moment in Trioclear (P < 0.05, P < 0.01); while a lingual force and Lab-inclination moment without significant change in Graphy (all P > 0.05). For 0.3 mm tipping, the amounts of labio-lingual forces and Lab-inclination moment did not differ among the three materials (all P > 0.05). However, at 0.6 mm tipping, Zendura exerted a greater labial force than Trioclear, while Graphy produced a lingual force (P < 0.01). Zendura and Trioclear generated a stronger Lab-inclination moment compared to Graphy (P < 0.01). Despite displaying unexpected force and moment directions, Graphy consistently exhibited the lowest absolute values among the groups.

Conclusions: Clinicians should select the appropriate aligner material based on the specific biomechanical requirements to prevent unexpected forces and moments.

Objective: Advancements in three-dimensional (3D) imaging technology have enhanced the accuracy and efficiency of clinical orthodontic diagnosis and treatment planning. This study aimed to evaluate craniofacial morphology in a Korean population using cone-beam computed tomography (CBCT).

Methods: CBCT images from 120 individuals (60 males and 60 females) were grouped into skeletal Classes I, II, and III types with normodivergence according to the ANB and sella-nasion plane to mandibular plane angles. Measurements of hard and soft tissues were performed in terms of sagittal, vertical, and transverse relationships, including asymmetry analysis and condylar position. The measurements were compared across different skeletal types including between males and females.

Results: Intergroup comparisons of hard and soft tissue measurements on 3D cephalograms showed statistical significance for several measurements of the sagittal relationship, occlusal plane angle and palatal depth in the vertical relationship, and maxillary intermolar width in the transverse relationship between Classes I, II, and III groups. Comparisons between skeletal Classes I, II, and III in males and females were consistent with these results.

Conclusions: 3D cephalometry can serve as a universal solution to the limitations of traditional two-dimensional cephalometry and decrease unnecessary radiation exposure. This study introduced a new 3D cephalometric measurement and Korean normative data, validating its effectiveness by comparing values across different skeletal malocclusion. These findings offer initial insights into craniofacial structure variations among numerous skeletal types and may prove valuable for future orthodontic diagnosis, treatment planning, and anthropological research using 3D cephalometry.

Objective: This study aimed to investigate the prevalence and characteristics of impacted teeth (ITs) in orthodontic patients at university dental hospitals in Korea.

Methods: This study included 14,774 patients who visited the Department of Orthodontics at 10 university dental hospitals in Korea between 2020 and 2022 and underwent orthodontic diagnosis. The prevalence and characteristics of ITs were investigated using orthodontic diagnostic records, radiographs, and diagnostic casts.

Results: The prevalence of ITs, excluding third molar impaction, in Korean orthodontic patients was 13.6% (n = 2,014). The prevalence of ITs in pediatric orthodontic patients was 24.5% (n = 1,614). Of these patients, 68.2% had one IT, 27.5% had two ITs, 24.3% had bilateral IT, and 75.7% had unilateral IT. The most frequent IT was the maxillary canine (50.1%), followed by the mandibular second molar (11.7%), and maxillary second premolar (9.6%). An abnormal eruption path (46.5%) was the most frequent etiology. Orthodontic traction after surgical exposure (70.6%) was the most frequent treatment option. Among the patients with ITs, 29.8% had other dental anomalies, such as tooth agenesis (8.7%), microdontia (8.0%), and supernumerary teeth (5.1%). Furthermore, 50.8% had complications such as cystic lesions (18.3%), transposition (17.7%), and root resorption (14.8%). Among the patients with maxillary canine impaction, 62.2% had labial maxillary canine impaction and 21.1% had palatal maxillary canine impaction.

Conclusions: The prevalence of ITs in Korean orthodontic patients at university dental hospitals was high, particularly in pediatric orthodontic patients.

Objective: To quantitatively analyze and compare the forces and moments generated by thermoformed polyethylene terephthalate glycol (PETG) and direct-printed TC-85 clear aligners (CAs), with various margin designs, during premolar rotation.

Methods: In total, 132 CAs were fabricated and divided into four groups (n = 33 per group). Group C consisted of thermoformed PETG aligners with a 2 mm gingival margin. Group E comprised direct-printed TC-85 aligners with equi-gingival margin, whereas Group G utilized direct-printed TC-85 aligners with 2 mm gingival margins. Finally, Group T featured direct-printed TC-85 aligners with an additional 1 mm thickness at the mesial embrasure. The forces and moments were measured using a 6-axis force/moment transducer at 2°, 3°, and 4° of rotation. All measurements were conducted at 37°C to simulate intraoral conditions. Forces were measured in the buccolingual, anteroposterior, and vertical directions, while moments were measured in the mesiodistal, buccolingual, and rotational planes.

Results: The PETG aligners (Group C) showed significantly increased buccal and posterior force across the rotation angles (P < 0.05), whereas the intrusive force remained consistent. In contrast, the TC-85 aligners maintained consistent forces across all rotation angles. Direct-printed aligners demonstrated significantly lower intrusive forces than PETG aligners (P < 0.001). Group T exhibited reduced unwanted forces while maintaining effective rotational moments. Furthermore, all direct-printed aligners showed more predictable force delivery patterns than thermoformed aligners.

Conclusions: Direct-printed TC-85 aligners demonstrated superior force consistency and reduced unwanted side effects compared with traditional PETG aligners. Although marginal design modifications did not significantly improve rotational efficiency, they effectively reduced unwanted intrusive forces.

Objective: To propose the utilization of virtual tooth models (VTMs) created by combining tooth root data from cone-beam computed tomography (CBCT) and crown data gathered through intraoral scanning to assess inter-root distance and angulation during orthodontic treatment when repeated radiographic monitoring becomes necessary.

Methods: Patients with planned dental implant placement in edentulous areas during or after orthodontic treatment and who underwent intraoral and CBCT scans at the pretreatment and posttreatment stages were selected. Tooth models were fabricated by merging intraorally scanned crowns with the corresponding CBCT-scanned roots from the pretreatment. Tooth positions posttreatment was estimated by integrating models into posttreatment intraoral scans. Moreover, the actual positions were obtained from posttreatment CBCTs. Discrepancies in the estimated and actual tooth positions, including inter-radicular distances and inter-root angulations, were compared.

Results: The minimum inter-radicular distance between two adjacent teeth demonstrated no significant difference between the estimated and actual tooth positions. The difference in inter-root angulation was not statistically significant. Most inter-radicular distances measured at each landmark revealed no significant differences between the estimated and actual tooth positions, except at the buccolingual midpoint of the cemento-enamel junction, where a slight discrepancy was observed.

Conclusions: The tooth position of VTMs demonstrated clinically acceptable accuracy compared to CBCT scans. Additionally, VTMs can benefit both clinicians and patients by enabling accurate assessment of the inter-radicular space for dental implant placement without repeated CBCT scans.

Objective: Considering the success of infrazygomatic mini-implants in conjunction with traditional braces, this study aimed to evaluate the efficacy of infrazygomatic mini-implants in en masse maxillary distalization utilizing clear aligner therapy.

Methods: In a three-dimensional finite element study, we evaluated the en masse maxillary dental distalization through the use of infrazygomatic mini-implants equipped with varying force-application arm lengths (0 mm, 4 mm, and 8 mm). Vertical, sagittal, and horizontal displacements were quantified.

Results: Intrusion was observed in the incisors at all force application arm lengths (0 mm, 4 mm, and 8 mm), with similar sagittal displacement tendencies and labial crown tipping. Among all maxillary teeth, only the canine exhibited distalization of both the crown and root. Distalization of the posterior teeth was achieved, with the greatest magnitude of distalization occurring at the 0-mm force application arm length, which was characterized by minimal tipping and reduced vertical movements compared to the other force application arm lengths.

Conclusions: The findings indicate that infrazygomatic mini-implants represent a viable approach for facilitating targeted tooth movement in clear aligners across various force-application arm lengths. These results may inform orthodontic treatment strategies in non-extraction cases.

Objective: Several studies have highlighted the toxic potential of bisphenol A (BPA), however, BPA release from orthopedic devices remains poorly investigated. Therefore, this study aimed to evaluate BPA levels in the saliva of children treated using Haas expanders.

Methods: Twenty-two children of both sexes aged 6-10 years who required rapid maxillary expansion were recruited. One week after placement of elastics to separate the permanent molars, orthodontic bands were adapted, and maxillary impressions were obtained using alginate impression material. Haas expanders were fabricated using a standardized amount of acrylic resin. The bands were cemented using Transbond Plus Light Cure Band (3M). Saliva samples were collected at five time points: before (T0) and 30 minutes (T1), 24 hours (T2), 1 week (T3), and 1 month (T4) after Haas expander installation. BPA levels were measured using ultra-high-performance liquid chromatography coupled with Tandem Mass Spectrometry. The results were evaluated using one-way analysis of variance with Tukey's post-hoc test (alpha = 5%).

Results: BPA levels were below the recommended tolerable daily intake (TDI) at all timepoints; however, salivary BPA levels at T1 (70.324 ng/mL ± 37.05) and at T2 (18.015 ng/mL ± 11.22) were significantly higher compared to that at T0 (0.475 ng/mL ± 0.27) (P < 0.05).

Conclusions: Salivary BPA levels significantly increased 30 minutes and 24 hours after Haas expander installation and return to baseline values after 1 week. BPA levels did not exceed the TDI, suggesting that the use of Haas expanders may be considered safe concerning BPA exposure in children.

Objective: Using finite element method (FEM) analysis of a clear aligner (CA), this study aimed to investigate the effects of varying the edentulous space on canine distal bodily movement during space closure following maxillary first premolar extraction.

Methods: FEM analysis was used to simulate distal canine bodily movement following maxillary first premolar extraction using CAs. Four CA designs for edentulous spaces were compared: no-pontic, full-pontic, half-pontic, and beam. Three-dimensional models of the tooth components and CA were created. The target was set at a 0.25-mm distal canine movement. Long-term tooth movement was simulated using an iterative calculation method.

Results: All the groups initially showed crown displacement, distal tipping, and distal rotation. Over time, the movement patterns differed in relation to the design. The no-pontic design exhibited the greatest displacement and tipping. The beam design exhibited the largest initial displacement but showed the lowest displacement and tipping thereafter. Full- and half-pontic designs yielded intermediate results. Significant force reduction was observed immediately after CA application, and was followed by a gradual decrease. The mean tooth-movement achievement rate was approximately 76.7%.

Conclusions: The edentulous space design of the CA substantially affected tooth-movement behavior. An iterative simulation is necessary to evaluate long-term tooth-movement patterns. The beam design demonstrated optimal suitability for bodily movement with minimal tipping. For optimal results, additional setup or overcorrection may be necessary.